Township of Greenwich, NJ Standards of Design

Block length. Blocks shall be not less than 50 feet long nor more than 1,300 feet long, except that blocks along major streets shall be not less than 800 feet long. Crosswalks up to 12 feet wide may be required by the Planning Board for blocks more than 1,000 feet long.

Block width. Blocks shall be wide enough for two tiers of lots and shall not be less than 200 feet wide.

Exceptions. Blocks in commercial and industrial districts may vary from the elements of design contained in this section if the nature of the use requires other treatment.

Lots.

Lot lines. Insofar as is practical, side lot lines shall be at right angles to straight streets and radial to curved streets.

Lot size. Minimum lot size shall be governed by Chapter 700, Zoning. When on-site sewage disposal is proposed, the Gloucester County Board of Health shall be requested to review the adequacy of the lots and facilities proposed and the appropriateness of the land for such purposes and may require such lot sizes as it deems necessary, which lot sizes shall not be greater than two acres.

Double frontage. Double-frontage lots are to be avoided and generally will not be permitted unless the lots are a minimum of 200 feet deep. Where the rear yards of double frontage lots abut major or intercommunity highways and the lots are entirely served by a separate residential service or neighborhood feeder street, their use may be required. In such cases, a planted buffer area and/or a fence shall be installed along the major or intercommunity highway frontage. The size and type of the fence or buffer shall conform to Township zoning regulations.

Grading and drainage. Blocks and lots shall be graded to secure proper drainage and to prevent the accumulation of stormwater in pools. A storm drainage system shall be constructed adequate to handle all surface and subsurface water reaching the tract or accumulating thereon. The owner must provide for any easements or improvements made necessary in the subdivision as a result of drainage problems which may arise from any adjacent area. Suitable evidence must be submitted to the Township to show that adequate provision for drainage has been included in the plan. In general, no open ditches will be approved. No topsoil shall be removed from the project site. Topsoil moved during the course of construction shall be redistributed within the subdivision so as to provide at least four inches of cover to all areas of the subdivision and shall be stabilized by seeding or planting. All grading and drainage plans shall be accomplished in accordance with the drainage standards included in § 610-37 hereof.

Residential parking. At least one off-street parking space behind the right-of-way line of the street and with access to a public street or alley shall be provided for each proposed dwelling unit. Where such access is to a major or secondary street, adequate turnaround space shall be provided on the lot to permit egressing vehicles to move forward into the traffic flow.

§ 610-34 Street, sidewalk and alley requirements.

Integration. The proposed street pattern shall be integrated with the Township plan of streets and shall be related to topography so as to produce usable lots and reasonable street grades.

Design and purpose. Streets shall be designed according to their function and laid out to preserve the integrity of their design. Streets shall be classified by function as follows:

Residential service streets. Streets providing direct access to residential structures and farms and intended primarily to serve the properties along them. Standards assume light traffic flow and street parking on two sides.

Neighborhood feeder streets. Streets connecting residential service streets, providing access to community facilities and intercommunity streets and intended primarily for the use of neighborhood traffic. Standards assume medium traffic flow and street parking on both sides.

Intercommunity streets. Streets connecting places of relatively dense settlement with each other and with major traffic streets and intended primarily for interneighborhood and commuter traffic. Standards assume relatively heavy traffic flow at high speeds. Street parking may or may not be assumed.

(4)

Major traffic streets. Streets serving large volumes of comparatively long-distance, high-speed traffic and intended primarily for intercity and commuter traffic.

(5)

Residential service and neighborhood feeder streets shall be located and designed to discourage through traffic.

Widths. Minimum street widths are as follows:

Type of Street	Right-of-Way (feet)	Cartway Width (feet)	Grading Width
Residential service	56	36	Full width
Neighborhood feeder	60	36	Full width
Intercommunity	60 to 80	36 to 60	Full width
Major traffic	Standards of State Department of Transportation

Continuations. New streets shall be laid out to continue existing streets at no reduction in width, provided that such continuations are both reasonable and practicable. When development is proposed along existing streets of insufficient width, sufficient additional width to conform with the above standards shall be required. In the event that a subdivision adjoins or includes existing Township streets that do not conform to widths as shown on the adopted Master Plan and/or Official Map or to the street width requirements of this chapter, additional land along either or both sides of said streets sufficient to conform to the right-of-way requirements shall be dedicated to the Township for the location, installation, repair and maintenance of streets, drainage facilities, utilities and other facilities customarily located in the street right-of-way. Such dedication shall be expressed on the plat as follows: "Street right-of-way easement granted to the Township of Greenwich permitting the Township to enter upon these lands for the purposes provided for and expressed in the Land Subdivision and Development Ordinance of the Township of Greenwich." This statement on an approved plat shall in no way reduce the subdivider's responsibility to provide, install, repair or maintain the facilities in the area dedicated by ordinance and/or as shown on the plat and/or as provided for by any maintenance or performance guaranties. If the subdivision is along one side only, 1/2 of the required extra width shall be dedicated. That portion of an existing street or road adjoining or included within the subdivision shall be improved, including excavating, grading, gravel base surfacing, storm drains, curbs, sidewalks, etc., in accordance with the road improvement standards of this chapter.

Names. Continuations of existing streets shall be known by the same name. Names for new streets shall not duplicate or closely resemble names of existing streets.

Access. Street layout shall make provision for access to all lots in the subdivision and to adjacent undeveloped areas whether on the same or an adjoining tract. The subdivider shall improve access streets to the limits of the subdivision.

Reserve strips. Reserve strips controlling access to the subdivision or to adjacent areas are prohibited.

Half streets. Provisions for half streets, except to complete existing half streets, is prohibited.

Highway frontage. If the subdivision abuts an existing or proposed major or secondary street, the Planning Board may require the use of reverse frontage or double frontage lots, as described above, and/or the use of a marginal service street along the edge of the highway but separated from it by a median strip at least five feet wide.

Railroad influence. When a subdivision abuts a railroad, streets crossing the railroad shall be kept to a minimum and shall be located to facilitate grade separation.

Dead-end streets. Dead-end streets are prohibited unless constructed as culs-de-sac. Culs-de-sac shall not be longer than 700 feet in length, measured to the center of the turnaround, which shall have a minimum right-of-way radius of 53 feet and a minimum cartway radius of 45 feet, measured to the inside curbline and shall be tangent wherever possible to the right side of the street. The Planning Board may require the turnaround to be placed on the tract boundary so as to provide for future extension of the street at full width. Drainage shall be away from the turnaround or provided for by storm sewers. If a cul-de-sac is of a temporary nature, provision shall be made for the reversion of the excess right-of-way to the adjoining properties when the street is extended.

Clear sight distance. Clear sight distance along the center lines of residential and neighborhood feeder streets shall be maintained at not less than 200 feet, along intercommunity streets at not less than 300 feet and along major streets at not less than 500 feet.

Grades. There shall be a minimum center-line grade of 1/2 of 1% and a maximum center-line grade of 6% on major or intercommunity streets and a maximum grade of 8% on other streets for short distances where no gentler slope is permissible. All grades below 1% shall require monolithic curb and gutter construction, and maximum grades within intersections shall be 3%.

Directional changes.

Changes in street direction shall be made by horizontal curves with a minimum radius of 500 feet for major streets, 300 feet for intercommunity streets and 100 feet for residential service and neighborhood feeder streets. These radii are to be measured from the inside curbline. If the aforesaid minimum radii do not provide the clear sight distances specified herein, the sight distance standards shall apply.

The following minimum tangent distances shall be introduced between reverse curves:

	Type of Street	Distance (feet)
	Residential service	100
	Neighborhood feeder	200
	Intercommunity	200
	Major traffic	As per New Jersey Department of Transportation Standards

When connecting street lines deflect from each other at any one point by more than 10°, they shall be connected by a curve with a radius conforming to standard engineering practice so that the minimum sight distances within the right-of-way shall be met.

Vertical curves. Vertical curves are required for changes in grade. All changes in grade where the algebraic difference in grade is 1% or greater shall be connected by a vertical curve having a length of at least 50 feet for each two-percent difference in grade or portion thereof and providing minimum sight distances of 200 feet for residential service and neighborhood feeder streets, 300 feet for an intercommunity street and 500 feet for a major traffic street.

Surface drainage. The slope of the crown on residential service and neighborhood feeder streets shall be more than 1/8 inch per foot and less than 1/2 inch per foot as directed by the Township Engineer. Unless special conditions warrant its use, drainage shall not be permitted in the center of the cartway.

Side slopes. Street cuts and street fills shall be provided with side slopes no steeper than one vertical to one and 1/2 horizontal. Where necessary, such slopes shall be sodded if required or suitably planted with perennial grasses or other vegetation to prevent gullying and erosion.

Shade trees. At least one shade tree for each 75 feet of frontage, on each side of the street, shall be provided. Such shade trees shall measure at least two inches in diameter at a point five inches above the ground at the time of planting. Wherever possible, developers shall preserve existing live trees, particularly those which measure five or more inches in diameter at the base of the trunk. Shade trees shall be located along residential streets so as not to interfere with sidewalk and utility installation and maintenance. Norway and silver maples are preferred; other species shall be as approved by the Township Shade Tree Committee. Cutting trees from a lot or filling around trees on a lot shall be permitted where it can be shown that grading or construction requirements necessitate removal of trees, in which case those lots shall be replanted with trees to reestablish the tone of the area and to conform with adjacent lots. Special attention shall be directed toward the preservation of major trees by professional means, i.e., tree wells, etc. The Planning Board may require such additional protective measures as are recommended by the Township Shade Tree Committee in its review of subdivision and site plans.

Street improvements. The road pavement minimum standard thickness shall be 3 1/2 inches of FABC-2 bituminous concrete applied to an eight-inch compacted gravel base on a subbase approved by the Township Engineer. The bituminous concrete shall be constructed the full width of the cartway from curb to curb and shall be applied in two courses. The first application shall be a two-inch-thick FABC (Mix No. 2) binder course and shall be applied prior to any issuance of certificates of occupancy for any dwelling facing the roadway in question. The finish course shall be one-and-one-half-inch-thick FABC (Mix No. 5) and shall be applied prior to the issuance of the last certificate of occupancy for the dwellings facing the roadway in question, but in no case later than one year after application of the binder course.

Intersections. Street intersections shall be designed according to the following standards:

No more than two streets cross at the same point. Street intersections shall be at right angles wherever possible, and intersections of less than 70°, measured at the center lines of the streets, will not be permitted.

Intersecting streets shall not enter into the same side of major traffic streets at intervals of less than 800 feet. Residential service and neighborhood feeder streets which enter a major traffic street from opposite sides should be directly opposite to each other or, if necessary, they may be separated by at least 200 feet between center lines, measured along the center line of the major traffic street.

The maximum grade within any intersection shall not exceed 3% unless the sight distance is such that a lesser grade is required. Approaches to any intersection shall follow a straight course within 100 feet of the intersection.

(4)

Curb radii at intersections shall be according to the following schedule of minimum lengths: 25 feet for residential service streets and alleys, 30 feet for neighborhood and secondary streets and 35 feet for major streets. Where streets of different categories intersect, requirements for the larger one shall apply as far as practicable. The street right-of-way line shall be parallel to the curbline. In zones where buildings are permitted to abut the right-of-way line, a diagonal cutoff may be employed.

(5)

Sight triangle easements shall be required at all intersections, in addition to the right-of-way width outlined above, in which no grading, planting or structure shall be erected or maintained more than three feet above the street center line, except for street signs, fire hydrants and light standards. The sight triangle is defined as that area outside the right-of-way which is bounded by the intersecting street lines and the straight line connecting the sight points, one each located on the two intersecting street center lines as follows: major traffic streets at 300 feet, intercommunity streets at 200 feet and residential service and neighborhood feeder streets at 90 feet. Where the intersecting streets are both major traffic streets, both intercommunity streets or one major street and one intercommunity street, two overlapping sight triangles shall be required, formed by connecting the sight points noted above with a sight point 90 feet on the intersecting street. Such easement dedication shall be expressed on the plat as follows: "Sight triangle easement granted to the Township of Greenwich for the purposes provided for and expressed in the Land Subdivision and Development Ordinance of the Township of Greenwich."

Street signs. Street signs shall be metal and on metal posts of the type, design and standard previously installed elsewhere in the Township. The locations of the street signs shall be determined by the Board, but there shall be at least two street signs furnished at each intersection. All signs shall be installed free of visual obstruction.

Sidewalks, curbs and driveway aprons. Sidewalks, curbs and driveway aprons shall be required for residential and commercial areas. State Highway Class B concrete (1:1.75:3.5) sidewalks shall be constructed in the right-of-way adjacent to the curbs. The location of sidewalks relative to planting strips shall be at the discretion of the Planning Board. Sidewalks shall be four feet wide by four inches thick and shall follow the required street profiles with no depression for driveways permitted. The Planning Board may require wider pavements in high-density areas and in commercial areas. The unpaved area between the curb and the property line shall be covered with four inches of topsoil and planted with grass seed or sod. Continuous permanent curbs of concrete shall be installed 18 inches high by six inches at the top and eight inches at the base with a six-inch face above the finished street grade. The six-inch to eight-inch taper shall be constructed entirely in the face of the curb. The slope of the driveway apron shall extend from the gutter line upward to the street side of the sidewalk only and shall not exceed 12.5%. Curb and driveway aprons shall not be poured monolithically. All driveway aprons and sidewalks, where they cross driveways, shall be six inches thick.

Alleys. The following standards shall apply to the design and location of alleys:

Public alleys shall not be permitted in residential developments except by permission of the Planning Board. Where public alleys are permitted in residential developments, they shall be 20 feet wide and paved for the full width. No part of any dwelling, garage or other structure may be located within 15 feet of the center line of a public alley.

Alleys serving commercial and industrial establishments are required unless other provisions for service are approved by the Planning Board. Alleys serving such establishments shall have a paved cartway of at least 20 feet. If it is impossible for an alley to extend fully throughout a block, the alley shall be provided with adequate turnaround at its closed end.

Material and construction standards. Material and construction standards for streets, curbs, gutters and sidewalks shall conform to the standards of this chapter, to the general construction and material specifications of Greenwich Township and amendments and revisions thereto, as approved by the Township Council, copies of which are available in the Greenwich Township Municipal Building and in the office of the Township Engineer; to the New Jersey Department of Transportation road specifications for cartway improvement, curbing and gutters; and to standards of the Township Engineer, when not otherwise designated in this chapter. Construction and installation of all facilities shall be subject to inspection by appropriate Township officials.

§ 610-35 Utilities.

Connection with sewer and water facilities. Except as provided in § 610-13D, connection to the Township sanitary sewer system and the Township water system shall be required in all subdivisions. Before occupancy of each dwelling, the water and sanitary facilities of the respective dwellings shall be ready for use and connected to a fully completed, functioning and approved sanitary sewer main and a potable water main.

Installation. Installation of all sewer, water and other utilities shall be in strict accordance with the engineering standards and specifications of the Engineer, municipal authority or other public utility concerned. All sanitary sewers shall be a minimum of eight inches in diameter. Under normal conditions, the pipe shall be vitrified clay pipe with compression joints; however, if certain conditions are present, the Township Engineer may require cement-lined ductile iron pipe. Water mains shall be a minimum of eight-inch diameter cement-lined ductile iron pipe with push-on joints. All water mains shall be looped or interconnected so as to form a continuous piping system. Dead-end mains will not be permitted; however, in the event that a dead end is unavoidable, an approved flushing device shall be installed. All water and sewer lines shall comply with the rules and regulations established by the Department of Environmental Protection of the State of New Jersey, as revised and amended to date.

Valves. The arrangement of valves shall be such that individual streets may be shut down and not more than three are necessary to shut off any one street or section. The number of homes affected by shutting off any one section shall be limited to approximately 35 dwellings.

Manholes. Manholes for sanitary sewers shall be spaced no more than 350 feet apart on straight runs, and there shall be a manhole at every point of change in direction or grade and at intersections of sewer mains.

Fire hydrants. Fire hydrants shall be located not more than 1,000 feet apart. The distance from any building frontage to a fire hydrant, however, shall be not more than 500 feet measured along the curb. The Planning Board, acting on the advice of the Fire Department, may require closer spacing of hydrants. In commercial and industrial areas, the Fire Department shall prescribe the location of hydrants. Hydrants shall not be placed in culs-de-sac but at the entrance to the same. All hydrants shall conform to those presently in use or as specified by the Township Engineer and shall have a six-inch inlet and valve in front of the same.

Easements. Where common utility lines are installed in or over undedicated land, a public easement of a minimum of 15 feet in width shall be required, provided that a larger width may be required on the recommendation of the Township Engineer to service the utilities located therein.

All electric, telephone and other public utility lines required to service any residential subdivision and the individual homes therein shall be installed underground, except for those lots or homes which can be served by existing aboveground lines. The Planning Board may waive or modify this requirement where it is determined to be impractical, in accordance with § 610-31C hereof.

§ 610-36 Environmental considerations; public areas and facilities provided; soil erosion and sediment control.

Preservation of natural features. Natural features, such as live trees, groves, brooks, hilltops, scenic points, historic landmarks and other natural community assets, shall be preserved whenever possible in designing any subdivision containing such features. Due consideration shall be given to the preservation of such natural features which enhance the beauty of the terrain, as well as to the laying out of adequate parks and playgrounds in residential areas for dedication to the Township or reservation for the common use of the public by deed, covenants or agreements which subject such areas to the control of the Township under conditions recommended by the Planning Board.

Drainage and soils study. In its review of subdivision plans, the Planning Board shall take into account the findings of the Greenwich Township Drainage and Soils Study, February 1974, prepared by McFarland-Johnson-Gibbons Engineers, Inc., Woodbury, New Jersey, as it applies to the area of proposed subdivision. Particular attention shall be directed to the Soils Inventory and Classification to determine the suitability of the soils for the proposed type of construction or use and to the drainage data with a view to eliminating or minimizing flooding and drainage problems.

Environmental impact statement. An environmental impact statement shall be submitted to the Planning Board prior to its approval of any subdivision for construction or use on lands for which an environmental impact statement is required by the New Jersey Wetlands Act[1] (Type-B permits) or by any other federal, state or local law or requirement of the Township of Greenwich, the County of Gloucester or the State of New Jersey which requires an environmental impact statement prior to development of environmentally sensitive areas.

[1]

Editor's Note: See N.J.S.A. 13:9A-1 et seq.

Public area characteristics. Areas set aside for recreational or school purposes shall be reasonably compact parcels placed to serve all parts of the subdivision with not less than 100 feet of frontage on a public street and not excessively irregular in terrain. Any areas that are set aside for recreation shall be so noted on the plans with the type of improvements and equipment proposed to be provided by the subdivider. The subdivider shall be responsible for providing for the improvements and any equipment that are shown on the plans prior to dedication to the Township.

Playground space. In subdivisions which provide or are intended to provide housing facilities for more than 50 families, the Planning Board shall consider the need for suitable open areas for recreation. Standards to be used by the Planning Board as guides in determining space needed for recreation shall be as follows:

	Families to be Served	Acres of Playground
	50 to 100	1.5
	101 to 200	2.75
	201 to 400	3.25
	401 to 600	4

Soil erosion and sediment control. The approval by the Planning Board or Township Council of a subdivision or site plan application which involves the disturbance of more than 5,000 square feet of land surface shall be conditioned upon certification by the local soil conservation district that the developer has submitted a plan for soil erosion and sediment control and that such plan meets the standards established by the State Soil Conservation Service. Copies of such plan shall be submitted to the Planning Board, and all improvements included in said plan or program shall also be included among the improvements secured by a surety bond or other form of performance guaranty as required under § 610-27 hereof.

§ 610-37 Drainage standards; residential site improvement standards.

[Amended 12-28-2000 by Ord. No. 34-2000]

In accordance with N.J.A.C. 5:21-7 and the following:

Each subdivision and/or site plan submitted to the Township Planning and/or Zoning Board shall be reviewed by the Planning Board Engineer to establish requirements to prevent adverse drainage conditions relating to drainage facility, roads or nearby properties. Water retention basins may be required for flood control and erosion control purposes in accordance with § 131-35 hereof.

On-site drainage easements. Drainage and flood control easements will be required across lands of the subdivider and/or developer where stormwaters flow directly or indirectly to or from a Township street, road or drainage structure.

Calculation basis.

Rainfall intensity. Provisions shall be made for a minimum time of concentration of 10 minutes for the following frequencies:

Minor inlets: two-year recurrence interval.

Inlets at low points: five-year recurrence interval.

(c)

Sump inlets: ten-year recurrence interval.

(d)

Stream structures with no headwaters: twenty-five-year recurrence interval.

(e)

Stream structures with headwaters: one-hundred-year recurrence interval.

Runoff determination.

In setting the value of the runoff coefficient "C," consideration will be given to the physical features of the drainage basin and the Planning Board's estimate of its future development, giving due consideration to Chapter 700, Zoning. In general, the value of the runoff coefficient "C" will fall within the following range:

	Classification	Runoff Factor "C"
	Park lands, golf courses, etc.	0.15 to 0.30
	Open residential, single family	0.30 to 0.50
	Multifamily residential and business	0.50 to 0.70
	Commercial and industrial	0.70 to 0.90

In computing runoff, the rational formula shall be used for all watersheds of five acres or less:

Q = CIA
Where:
	Q	=	Volume, in cubic feet per second
	C	=	Runoff factor
	I	=	Intensity of rainfall, in inches per hour
	A	=	Watershed area, in acres

(c)

Where the watershed exceeds five acres but is less than one square mile, the runoff shall be calculated using the Soil Conservation Service Method. Special Report No. 38 as prepared by the United States Geological Survey shall be used in computing the runoff for all watersheds equal to or greater than one square mile.

Pipeline and open channel hydraulics. All storm sewers shall serve two major functions, to carry the maximum discharge for which it is designed and to transport suspended solids in such a manner that deposits in the sewer are kept to a minimum.

Open channel design.

Permissible design velocities, feet per second.

	Excavation Material	Velocity
	Fine sand to firm loam	2.5 to 3.5
	Stiff clay to hardpan	3.75 to 6
	Concrete-lined ditch	15
	Velocity shall be controlled by the use of check dams or ditch banks and shall be protected by the use of sod, riprap or paving, as design velocity dictates.

Discharge flow: Manning's formula.

Values of "n," Manning's formula:

Best concrete-lined ditch: 0.015.

Best unlined ditch: 0.025.

(c)

Fair to poor natural streams and watercourses: 0.03 to 0.15.

Pipe flow design criteria. All stormwater piping shall be designed using Manning's formula for flow in pipes.

Pipes shall be considered flowing full at maximum capacity.

Minimum design velocity at flowing-full condition shall be 3 1/2 feet per second.

Friction factor "n" shall be 0.012 for circular cross section nonporous concrete pipe. Other cross sections or pipe materials shall have commensurate friction factors as may be approved by the Township Engineer.

Sewer pipe; type required. Pipe used shall be reinforced concrete pipe, Class III, Wall B with O-ring-type joint, unless otherwise directed by the Township Engineer. All pipe shall be installed with not less than two feet depth of cover over the top of the pipe. If the pipe is to be installed with less than two feet of cover, proper engineering mechanics calculations shall be submitted. These calculations shall indicate that an HS-20 wheel load can be safely supported by the pipe within the limits of a 0.1 "D" flexure crack.

Line transitions. In pipe sizes of 48 inches or less in diameter, all transitions in slope, horizontal direction, junctions and change in pipe sizes shall be confined to manholes, catch basins, or other accessible structures designed for one or more of these purposes. In pipe lines 48 inches and larger, vertical and horizontal deflections may be accomplished by using one-hundred-foot or greater radius curves.

Catch basin and manhole type required. Catch basins and manholes shall be constructed in accordance with New Jersey State Standard Specifications for Road and Bridge Construction, 1961 Edition, including amendments thereto. The casting curb head height shall be two inches greater than the curb height specified. Castings shall conform to New Jersey State Standards.

Inlet spacing. Inlet spacing shall not exceed 600 feet or a design inlet flow of 55 cubic feet per second, whichever condition shall be more stringent. Access manholes shall be spaced at eight-hundred-foot intervals, maximum, through rights-of-way and at sewer junctions where there are no catch basins. Discharge and collection systems shall not be designed for inlet heads under any circumstances.

Intersections and gutters. A sufficient number of catch basins shall be installed at each street intersection to avoid the use of rocker gutters or gutter overflow. Catch basins shall also be installed at all low points in the street grade.

Headwalls. The ends of pipe starting or terminating in open ditches shall have headwalls. The size, shape and type of materials to be used for headwalls shall be as approved by the Township Engineer. When outlet velocities will cause erosion, energy dissipaters will be required.

Stormwater discharge. No subdivided tract, either during construction or after development, shall discharge stormwater to contiguous neighbors in a quantity, in cubic feet per second, that exceeds the tract discharge in its natural undeveloped stage. The quantity of natural and developed discharge shall be determined utilizing natural and developed runoff parameters and an intensity of 6.0 inches of rainfall in 24 hours. The excess stormwater shall be suitably detained and discharged at the preconstruction quantity. The detention devices' performance shall also be investigated for storms of lesser frequency. If no watercourse is available for discharge, a retention basin with groundwater recharge may be permitted after the applicant has demonstrated the feasibility of successful operations.

Outlet trenches.

The installation of subbase outlet trenches will be required in roadways at all inlets as follows:

Low points: two outlet trenches per each inlet.

Intermediate inlets: one per each inlet installed on the upgrade side of the inlet.

Subbase outlet trenches may be waived if the developer can demonstrate that the subgrade soils will adequately dissipate any water entering the subbase of the roadway.

Detention basins in residential subdivisions should be designed as an open space amenity and comply with the following:

The maximum side slope of any basin shall be 3:2 with 4:1 recommended, and shall be constructed with side slope protection consisting of a minimum of four inches of topsoil and sod, pegged in place.

The minimum depth from the bottom of any infiltration basin to the seasonal high water table (SHWT) shall not be less than two feet.